Measuring of the volume or level of material in a container is reasonably well known in the art. See e.g. U.S. Pat. No. 2,946,991 to Lindenberg and U.S. Pat. No. Re 27,829 to Tiffany. However, none of these prior art level or volume measuring devices includes means for adjustably presetting the apparatus to negate the effects of residual capacitance in the probe. Such residual capacitance effects will cause a measurable indication on a meter or other indicator even when no material is presently in the container if not compensated for by operation of the circuitry. Further, an indication of a critical level or volume is also desirous, with such level indicating means being also adjustable depending on the result desired. The Patent to Hile et al, U.S. Pat. No. 4,001,676 discloses a level warning detector, but does not include means for simply and easily enabling the adjustment of said means.